Self-tanning dihydroxyacetone formulations having improved stability and providing enhanced delivery

Abstract

A composition is provided which is useful for self-tanning skin coloring and is characterized by improved stability, which comprises from about 0.5% to about 20.0% by weight, based on total weight of said composition, of a self-tanning skin coloring agent subject to chemical instability, which is preferably dihydroxyacetone; from about 2.0% to about 40.0% by weight of a polyethoxyglycol, which is preferably ethoxydiglycol; and from about 0.1% to about 15.0% by weight of a polyol comprising a polyhydric compound having at least three hydroxyl groups and at least three carbon atoms, which is preferably D-sorbitol. The self-tanning composition may further optionally contain from about 0.1% to about 8.0% by weight of a water soluble dihydroxyl compound having at least two, and up to eight carbon atoms, which is preferably ethylene glycol; and the self-tanning composition may still further optionally contain an acidifying agent in amount sufficient to maintain the pH of said total composition at from about 3.5 to about 4.5, which is preferably sorbic acid. Cosmetologic products and methods of tanning are also provided.

Description

The present invention is in the broader technical field relating to compositions for the topical application of active agents to the skin with sufficient penetration to be efficacious. Such active agents can be cosmetic agents or therapeutic agents; thus, the disciplines of pharmacology and cosmetology are involved. The present invention is, further, in the narrower technical field relating to cosmetic compositions where the active agent is a sunless tanning compound, in particular dihydroxyacetone, which is delivered by topical application of a cosmetic product formulation containing dihydroxyacetone to the skin of a user of said product. In this narrower technical field, it is appreciated that desirable product formulations have sufficient stability and skin penetration to provide an even tan of the desired color in a timely fashion.The prevailing cultural esthetic among fair-skinned persons in many countries and places is to have a skin which is tanned, i.e., which has a light ye...

AI Technical Summary

Problems solved by technology

However, the reversal of said chemical instability is even more pronounced when the polyol component is used together with the further key component comprising a dihyroxyl compound.

However, inexplicably the pH of the formulation mixture soon begins to drop, i.e., the mixture becomes more acidic and the self-tanning skin coloring agent, especially dihydroxyacetone, becomes unstable.

The formulation mixture is observed to disintegrate with the formation of organic acids and formalin, leading to the creation of disagreeable odors and unacceptable colors in the formulation mixture.

Thus, one of the serious disadvantages of dihydroxyacetone is an unacceptably short shelf life.

While this is a desirable property with respect to preparing formulations with dihydroxyacetone, it also creates a problem because it thereby exposes dihydroxyacetone to the action and affects of various agents, transports it into many unintended environments, and makes its isolation difficult.

Another serious problem facing the cosmetic formulator or other artisan attempting to devise a useful composition containing dihydroxyacetone is the substantial oxidizing capacity of dihydroxyacetone, since it can lead not only to undesired activity once applied to the skin of the ultimate consumer, but can also lead to difficulties in terms of its interaction with the other components with which it is formulated.

At the lower pH's especially, dihydroxyacetone becomes very unstable, which makes its formulation and ultimate use environment problematic to manage.

Another source of instability in dihydroxyacetone is its particular sensitivity to the degradative activities of bacteria and other microorganisms.

Methyl glyoxal is also responsible for the production of an undesirable orange pigmentation when dihydroxyacetone is applied to the skin and is not present in a stabilized form.

However, alkalizing agents which contain active amine groups, such as diethanolamine and trolamine, not be used.

However, it has been discovered that such compounds are troublesome because they undergo a Maillard reaction with the dihydroxyacetone to form different side products which have undesirable properties.

For example, anitmicrobial preservatives which contain active amine groups are not suitable.

Thus, it would normally be unacceptable to select a metal oxide or other active salt such as black iron oxide, chromium oxides, yellow and red iron oxides, titanium dioxide, ultramarines (aluminosilicate polysulfides), manganese pyrophosphate, and ferric blue . . . . However, it is possible to use such pigments as carbon black and certain organic dyes such as cochineal carmine, azo dyes, and anthraquinone dyes; natural, colored cosmetically active substances which mask the hue produced by dihydroxyacetone or other self-tanning agent, such as the blue azulenes guajazulene and chamuzulene, the yellow flavanoids rutin and quercetin, erythrosin, bengal rose, phloxin, cyanosin, daphinin, eosin G, cosin 10B, and Acid Red 51.

However, emollients based on compounds which contain active amine groups are unsuitable.

Propylene oxide ethers of glycerin and hydrolyzed corn starch are suitable for use, but humectants based on vegetable protein are not, and these include hydrolyzed wheat protein / wheat oligosaccharides, hydrolyzed corn protein hydrolyzed wheat gluten, hyrolyzed yeast protein, hydrolyzed vegetable protein, hydrolyzed soy protein, hydrolyzed rice protein, and hydrolyzed potato protein.

The cyclic ketal is stable but incapable of producing the self-tanning reaction on the skin.

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